1. Field of the Invention
The present invention relates to a surgical treatment for dysphonia and its requisite device for carrying out the treatment. More specifically, the invention relates to a device useful for the surgical treatment of thyroplasty type II, which has been known as Isshiki's operation, and a method of treating dysphonia with use of the device.
2. Discussion of the Related Art
The causes for difficulty of voice production or hoarse voice are multiple, for example vocal abuse, excessive smoking, vocal tumors such as polyp and cancer, and vocal fold mobility disturbance. Voice disturbance due to vocal abuse can be treated effectively by simple vocal rest for a week for instance, and dysphonia resulting from vocal tumors can be managed by surgical removal of the tumor. However, disphonia associated with vocal fold mobility disturbance, such as paralysis producing imperfect closure of the glottis, or conversely, excessively tight closure of the glottis on phonation is too complicated to handle by the above-mentioned treatments.
Spasmodic dysphonia, which is caused by an excessively tight closure of the glottis, was first treated by recurrent laryngeal nerve section, with some success, though proved later to be only temporary (see Dedo H H. Recurrent laryngeal nerve section for spastic dysphonia. Ann Otol Rhinol Laryngol. 1976; 85: 451–459). Recently, a treatment by administrating botulinum toxin to muscles of a patient was proposed as a replaceable therapy of the nerve section (see, Brin MF et al.: Treatment of spasmodic dysphonia (laryngeal dystonia) with local injections of botulinum toxin: in review and technical aspects. In A. Blitzer et al, eds.; Neurologic Disorders of the Larynx. New York, N.Y.: Thieme Medical Publishers 1992; 214–228). This approach with the administration of botulinum toxin is currently in most frequent use, however, there is a problem that the clinical efficacy of botulinum toxin dose not last in long term. Due to the fact that botulinum toxin induces temporary paralysis of the muscle where the toxin is injected, the effect of blocking the nerve impulse from the injection of the botulinum toxin gradually dwindles, usually diminishing in about 3 to 4 months. As a result, the patient requires an injection of the toxin every three to six months. To make matters worse, the repetitive injections of the toxin are associated with a serious problem that determination of the dose and injection site of the toxin is not easy due to great individual variation such as weight, age, and responsiveness to the therapy.
On the other hand, one of the inventors proposed a surgical intervention into the thyroid cartilage. As shown in FIG. 4, a part of the thyroid cartilage 11 forms the Adam's Apple. The proposed surgical treatment is called as thyroplasty type II and described in the articles “Isshiki N. et al. Midline lateralization thyroplasty for adductor spasmodic dysphonia. Ann Otol Rhinol Laryngol 2000:109:189–193”, and others.
The conventional surgical treatment of thyroplasty type II is carried out according as procedures in FIGS. 5 to 8. First, the thyroid cartilage 11 is vertically incised at the midline thereof (see FIG. 5), and the incised edges 11a, 11a are pulled laterally by hooks 12, 12 (see FIG. 6), so that the vocal folds are also pulled laterally, preventing excessive tight closure of the glottis.
After that, as shown in FIG. 7, a silicone prosthesis 13 is prepared. The silicone prosthesis 13 consists of a pair of wings 13b,13b and a prominence 13a between the wings 13b,13b, the prominence 13a being capable of fitting the width (W) of the groove 14 created by separation of the cartilage. The prominence 13a is inserted in the groove 14 and the pair of wings 13b,13b are fixed to the thyroid cartilage 11 by sutures, thereby securing the width (W) which is optimal distance for phonation. FIG. 8 illustrates that the two silicone prostheses 13,13 are fixed to the cartilage 11 at the upper and lower portions thereof.
This surgical procedure proved to be effective in relieving the vocal strain on phonation, recovering their normal voice in 26 patients operated on, with one exception who had other dystonia too. No recurrences were noted in any patient. The longest follow-up period is 4 years.
However, the procedure of fitting in and stabilizing the silicone prosthesis 13 in the groove 14 of the incised thyroid cartilage requires a surgical expertise. This technical difficulties prevented popularization of the surgical treatment of thyroplasty type II.
There is a further technical difficulty with the surgical treatment. Since the thyroid cartilage is located in the anterior middle of the neck, it is desirous that any protrusion after the procedure of fixing the silicone prosthesis 13 to the thyroid cartilage 11 is inconspicuous, especially in women. To meet the requirement, the silicone prosthesis 13 having small and thin wings 13a, 13a is preferably employed. On the other hand, numerous sutures are required in order to fix the prosthesis to the cartilage for long-term widening the incised edges of the thyroid cartilage, despite that such numerous sutures may cause damage to the edges of the incised cartilage and/or the thin silicone wings.